Such exhaust flap devices can be used in the field of exhaust gas recirculation, heat recovery, or as exhaust brakes for the increase of differential pressure. High demands are posed on these exhaust flap devices to provide functional reliability due to the high temperatures. In this regard, both the flap body itself with its bearing and the actuator for driving the flap must be designed for this thermal stress. For this reason, use is often made either of temperature-insensitive actuators, such as vacuum actuators, for driving such flaps, or the actuator is arranged at a sufficient distance from the hot exhaust gas. Bearings with high thermal load capacities, such as, for example, ceramic bearings are additionally used to support the flap shaft.
The use of low-cost materials and of electromotively driven actuators is made possible by the fact that the flap housing is cooled and the actuator is thermally separated from the flap housing.
DE 602 08 832 T2 describes an exhaust gas recirculation device in which a flap body for controlling the exhaust gas flow is arranged upstream of a heat exchanger. The housing of the exhaust flap is provided with a coolant jacket which is in fluid communication with the coolant jacket of the heat exchanger via a coolant. The actuator of the flap is fastened on the outside of the housing and is thermally separated from the exhaust gas duct by means of the coolant jacket.
An exhaust gas recirculation device with a double flap is also described in DE 10 2006 054 041 B3 which is driven by an electric motor that is surrounded by a spiral-shaped coolant duct. No cooling of the flaps is provided.
EP 1 420 158 A2 describes an exhaust gas recirculation device in which an electric motor and a flap driven by the electric motor are arranged in a common housing. The flap is surrounded by a coolant duct, wherein one of the cooling ducts is arranged between the flap and the electric motor.
The cooling of these known devices is, however, often insufficient so that excessive thermal stress on the bearings, the electric motor, or the electronics of the electric motor occurs. Eddy water areas with insufficient flow are further not avoided, which also reduces the cooling effect.